Ever since I was a premie, overheating and thermo-regulation have been my arch-enemies. On a few occasions, I’ve been hospitalized for heat stroke symptoms, and the symptoms hit suddenly and without warning. I’m extremely lucky I didn’t smash my skull on the ground after the collapses.

To delve into this handicap, I even became a test subject at Stanford University in 2005.

It was as fun as it looks (I’ll share videos another time, as they’re hilarious):

After each session, I was so incapacitated that I couldn’t do any work for 8-12 hours. I often had to simply go home and sleep, even at 11am. These issues led me to eventually leave the study.

Heat is serious fucking business, m’kay?

People can die from excessive heat (sauna example here, recent running death here), so read these warnings carefully…

TIM’S DISCLAIMER ON THIS POST:

Please don’t be stupid and kill yourself. It would make us both quite unhappy. Consult a doctor before doing anything described in this post or on this blog.

BIGGER LAWYER DISCLAIMER:

The material on this blog is for informational purposes only. As each individual situation is unique, you should use proper discretion, in consultation with a health care practitioner, before undertaking the protocols, diet, exercises, techniques, training methods, or otherwise described herein. The author and publisher expressly disclaim responsibility for any adverse effects that may result from the use or application of the information contained herein.

OK, will all that out of the way, here we go.

Consider looking at this piece as what elite athletes are likely to augment to their training and drug regimens.

The following is a guest article by Rhonda Perciavalle Patrick, Ph.D., who works with Dr. Bruce Ames of the Ames carcinogenicity test, the 23rd most-cited scientist in all fields between 1973 and 1984. Dr. Patrick also conducts clinical trials, performed aging research at Salk Institute for Biological Studies, and did graduate research at St. Jude Children’s Research Hospital, where she focused on cancer, mitochondrial metabolism, and apoptosis.

Enjoy!

And if you have any experiences with using heat, cold, or other environmental factors to improve performance; or if you’ve suffered from them; I’d love to hear about it all in the comments. Ditto for any factual corrections.

Enter Rhonda

For the most part, people don’t like to get hot.

The massive indoor climate control systems and pleasantly chilled water fountains found in most gyms speak to this fact. There are some exceptions — Bikram yoga, for example — but they’re few and far between.

But here’s the surprise: increasing your core temperature for short bursts is not only healthful, it can also dramatically improve performance.

This is true whether it’s done in conjunction with your existing workout or as an entirely separate activity. I’m going to explain how heat acclimation through sauna use (and likely any other non-aerobic activity that increases core body temperature) can promote physiological adaptations that result in increased endurance, easier acquisition of muscle mass, and a general increased capacity for stress tolerance. I will refer to this concept of deliberately acclimating yourself to heat, independent of working out, as “hyperthermic conditioning.”

I’m also going to explain the positive effects of heat acclimation on the brain, including the growth of new brain cells, improvement in focus, learning and memory, and ameliorating depression and anxiety. In addition, you’ll learn how modulation of core temperature might even be largely responsible for “runner’s high” via an interaction between the dynorphin/beta-endorphin opioid systems.

The Effects of Heat Acclimation on Endurance

If you’ve ever run long distances or exercised for endurance, it’s intuitive that increased body temperature will ultimately induce strain, attenuate your endurance performance, and accelerating exhaustion. What might not be as intuitive is this: acclimating yourself to heat independent of aerobic physical activity through sauna use induces adaptations that reduce the later strain of your primary aerobic activity.

Hyperthermic conditioning improves your performance during endurance training activities by causing adaptations, such as improved cardiovascular and thermoregulatory mechanisms (I will explain what these mean) that reduce the negative effects associated with elevations in core body temperature. This helps optimize your body for subsequent exposures to heat (from metabolic activities) during your next big race or even your next workout.

Hyperthermic conditioning optimizes blood flow to the heart, skeletal muscles, skin, and other tissues because it increases plasma volume. This leads to endurance enhancements in your next workout or race, when your core body temperature is once again elevated.

Being heat acclimated enhances endurance by the following mechanisms…

It increases plasma volume and blood flow to the heart (stroke volume).2,5 This results in reduced cardiovascular strain and lowers the heart rate for the same given workload.2 These cardiovascular improvements have been shown to enhance endurance in both highly trained and untrained athletes.2,5,6

It increases blood flow to the skeletal muscles, keeping them fueled with glucose, esterified fatty acids, and oxygen while removing by-products of the metabolic process such as lactic acid. The increased delivery of nutrients to muscles reduces their dependence on glycogen stores. Endurance athletes often hit a “wall” (or “bonk”) when they have depleted their muscle glycogen stores. Hyperthermic conditioning has been shown to reduce muscle glycogen use by 40%-50% compared to before heat acclimation.3,7 This is presumably due to the increased blood flow to the muscles.3 In addition, lactate accumulation in blood and muscle during exercise is reduced after heat acclimation.5

It improves thermoregulatory control, which operates by activating the sympathetic nervous system and increasing the blood flow to the skin and, thus the sweat rate. This dissipates some of the core body heat. After acclimation, sweating occurs at a lower core temperature and the sweat rate is maintained for a longer period.2

So what sort of gains can you anticipate?

One study demonstrated that a 30-minute sauna session two times a week for three weeks POST-workout increased the time that it took for study participants to run until exhaustion by 32% compared to baseline.4

The 32% increase in running endurance found in this particular study was accompanied by a 7.1% increase in plasma volume and 3.5% increase in red blood cell (RBC) count.4 This increased red blood cell count accompanying these performance gains feed right back into those more general mechanisms we talked about earlier, the most obvious of which being: more red blood cells increase oxygen delivery to muscles. It is thought that heat acclimation boosts the RBC count through erythropoietin (EPO) because the body is trying to compensate for the corresponding rise in plasma volume.4

(Note from Tim: If “EPO” sounds familiar, it’s because it’s commonly injected by Tour de France competitors. More on that here.)

In other words, hyperthermic conditioning through sauna use doesn’t just make you better at dealing with heat; it makes you better, period. I do want to mention that while these gains were made with a small sample size (N=6) some of the later studies that I point out reinforce this conclusion.

The Effects of Hyperthermic Conditioning on Muscle Hypertrophy (Growth)

Exercise can induce muscular hypertrophy. Heat induces muscular hypertrophy. Both of these together synergize to induce hyper-hypertrophy.

Here are a few of the basics of how muscle hypertrophy works: muscle hypertrophy involves both the increase in the size of muscle cells and, perhaps unsurprisingly, an accompanying increase in strength. Skeletal muscle cells do contain stem cells that are able to increase the number of muscle cells (TIM: called “hyperplasia”) but hypertrophy instead generally involves an increase in size rather than number.

So what determines whether your muscle cells are growing or shrinking (atrophying)?

A shift in the protein synthesis-to-degradation ratio…and an applied workload on the muscle tissue (of course). That’s it.

At any given time your muscles are performing a balancing act between NEW protein synthesis and degradation of existing proteins. The important thing is your net protein synthesis, and not strictly the amount of new protein synthesis occurring. Protein degradation occurs both during muscle use and disuse. This is where hyperthermic conditioning shines: heat acclimation reduces the amount of protein degradation occurring and as a result it increases net protein synthesis and, thus muscle hypertrophy. Hyperthermic conditioning is known to increase muscle hypertrophy by increasing net protein synthesis through three important mechanisms:

Exercise induces both protein synthesis and degradation in skeletal muscles but, again, it is the net protein synthesis that causes the actual hypertrophy. When you exercise, you are increasing the workload on the skeletal muscle and, thus, the energetic needs of your muscle cells. The mitochondria found in each of these cells kick into gear in order to help meet this demand and start sucking in the oxygen found in your blood in order to produce new energy in the form of ATP. This process is called oxidative phosphorylation. A by-product of this process, however, is the generation of oxygen free radicals like superoxide and hydrogen peroxide, which is more generally referred to simply as “oxidative stress”.

For this reason, any means of preventing exercise-induced oxidative protein damage and/or repairing damaged proteins, while keeping the exercise induced protein synthesis, will ultimately cause a net increase of protein synthesis and therefore will be anabolic.

Heat shock proteins (or HSPs), as the name implies, are induced by heat and are a prime example of hormesis. Intermittent exposure to heat induces a hormetic response (a protective stress response), which promotes the expression of a gene called heat shock factor 1 and subsequently HSPs involved in stress resistance.

HSPs can prevent damage by directly scavenging free radicals and also by supporting cellular antioxidant capacity through its effects on maintaining glutathione.8,9

Okay, let’s take a step back from the underlying mechanisms and look at the big picture of heat acclimation in the context of increasing muscle hypertrophy:

It has been shown that a 30-minute intermittent hyperthermic treatment at 41°C (105.8°F) in rats induced a robust expression of heat shock proteins (including HSP32, HSP25, and HSP72) in muscle and, importantly, this correlated with 30% more muscle regrowth than a control group during the seven days subsequent to a week of immobilization.8 This HSP induction from a 30-minute intermittent hyperthermic exposure can persist for up to 48 hours after heat shock.8,9 Heat acclimation actually causes a higher basal (such as when not exercising) expression of HSPs and a more robust induction upon elevation in core body temperature (such as during exercise). 111213 This is a great example of how a person can theoretically use hyperthermic conditioning to increase their own heat shock proteins and thereby reap the rewards.

Heat Stress Triggers A Massive Release of Growth Hormone

Another way in which hyperthermic conditioning can be used to increase anabolism is through a massive induction of growth hormone. 1415, 1 Many of the anabolic effects of growth hormone are primarily mediated by IGF-1, which is synthesized (mainly in the liver but also in skeletal muscle and other tissues) in response to growth hormone. There are two important mechanisms by which IGF-1 promotes the growth of skeletal muscle:

It decreases protein degradation via inhibition of the FOXO pathway.16

Mice that have been engineered to express high levels of IGF-1 in their muscle develop skeletal muscle hypertrophy, can combat age-related muscle atrophy, and retained the same regenerative capacity as young muscle. 17,18 In humans, it has been shown that the major anabolic effects of growth hormone in skeletal muscle may be due to inhibition of muscle protein degradation (anti-catabolic), thereby increasing net protein synthesis.16 In fact, growth hormone administration to endurance athletes for four weeks has been shown to decrease muscle protein oxidation (a biomarker for oxidative stress) and degradation by 50%. 19

My point is good news. You don’t need to take exogenous growth hormone. Sauna use can cause a robust release in growth hormone, which varies according to time, temperature, and frequency.1,15

For example, two 20-minute sauna sessions at 80°C (176°F) separated by a 30-minute cooling period elevated growth hormone levels two-fold over baseline.1,15 Whereas, two 15-minute sauna sessions at 100°C (212°F) dry heat separated by a 30-minute cooling period resulted in a five-fold increase in growth hormone.1,15 However, what’s perhaps more amazing is that repeated exposure to whole-body, intermittent hyperthermia (hyperthermic conditioning) through sauna use has an even more profound effect on boosting growth hormone immediately afterward: two one-hour sauna sessions a day at 80°C (176°F) dry heat (okay, this is a bit extreme) for 7 days was shown to increase growth hormone by 16-fold on the third day.14 The growth hormone effects generally persist for a couple of hours post-sauna.1 It is also important to note that when hyperthermia and exercise are combined, they induce a synergistic increase in growth hormone. 20

Increased Insulin Sensitivity

Insulin is an endocrine hormone that primarily regulates glucose homeostasis, particularly by promoting the uptake of glucose into muscle and adipose tissue. In addition, insulin also plays a role in protein metabolism, albeit to a lesser degree than IGF-1. Insulin regulates protein metabolism in skeletal muscle by the two following mechanisms:

For this reason, hyperthermic conditioning may also lend itself to promoting muscle growth by improving insulin sensitivity and decreasing muscle protein catabolism. Intermittent hyperthermia has been demonstrated to reduce insulin resistance in an obese diabetic mouse model. Insulin resistant diabetic mice were subjected to 30 minutes of hyperthermic treatment, three times a week for twelve weeks. This resulted in a 31% decrease in insulin levels and a significant reduction in blood glucose levels, suggesting re-sensitization to insulin.10 The hyperthermic treatment specifically targeted the skeletal muscle by increasing the expression of a type of transporter known as GLUT 4, which is responsible for the transporting of glucose into skeletal muscle from the bloodstream. Decreased glucose uptake by skeletal muscle is one of the mechanisms that leads to insulin resistance.

Relevance for Muscle Injury

Animal studies using rats have shown that a 30-minute and 60-minute hyperthermic treatment at 41°C (105.8°F) attenuates hindlimb muscle atrophy during disuse by 20% and 32%, respectively.9,25 In order to return to a hypertrophic state after injury, muscle regrowth (“reloading”) must occur. Muscle reloading, while important for hypertrophy, induces oxidative stress particularly after periods of disuse, which slows the rate of muscle regrowth. A 30-minute hyperthermic treatment at 41°C (105.8°F) increased soleus muscle regrowth by 30% after reloading as compared to non-hyperthermic treatment in rats.8 The effects of whole body hyperthermia on preventing muscle atrophy and increasing muscle regrowth after immobilization were shown to occur as a consequence of elevated HSP levels.8,9,25

During injury, you may be immobilized but you don’t have to be very mobile to sit in the sauna a few times a week to boost your HSPs! This is a clear win in the injury and recovery department. Remember, hyperthermic conditioning (from sauna use) results in an elevation in HSP levels under normal conditions and leads to an even greater boost during exercise (or when core body temperature is elevated).11-13

Relevance for Rhabdomyolysis

Hyperthermic conditioning may also be able to protect against rhabdomyolysis (muscle breakdown due to severe muscle overuse) through the induction of HSP32 also known as heme oxygenase 1. 26, 27

Rhabdomyolysis releases myoglobin, a byproduct from broken down muscle tissue, into the bloodstream, which can cause kidney failure. (TIM: CrossFitters, watch your CPK levels after glute-ham ab work. If you can’t do long planks with your feet against a wall, don’t do hyper-extended ROM, ballistic ab work.)

Since myoglobin is a heme-containing protein, HSP32 (heme oxygenase 1) can rapidly degrade myoglobin before it has toxic effects on the kidney.26,27 In fact, induction of HSP32 in rats has been shown to protect against rhabdomyolysis in rats.26 This function of HSP32 is very different than the classical role of HSPs in preventing protein degradation. Again, heat acclimation causes a higher basal expression of HSPs and a more robust expression upon heat stress.11-13 The more heat acclimated your body is (the pre-conditioning is the key here), the higher your HSP32 expression will be during physical activity and this will protect your kidneys from the toxic myoglobin breakdown product.

That’s a sweet deal.

Longevity

In flies and worms, a brief exposure to heat treatment has been shown to increase their lifespan by up to 15% and it’s been shown that this effect is specifically mediated by HSPs. 28,29,30

While studying the effects of something like hyperthermic conditioning on longevity is inherently hard in humans (obviously), there have been some preliminary positive associations with variations in the HSP70 gene associated with increased expression and longevity. 31

Effects of Heat Stress on The Brain

One of the ways that the brain responds to injury on the cellular level is increased HSP production.

This includes ischemic injury (i.e. stroke), traumatic injury, and excitotoxicity (epileptic). 32 What complicates things, however, in the context of “hyperthermic conditioning” (or deliberate heat acclimation) is that while on the one hand hyperthermia has been shown to reduce the frequency of seizures and the damage they cause post-conditioning, hyperthermia can actually increase the damage caused by seizures if they occur during a period of heat stress. In other words, the stress and its damaging effects are additive. 3334

That (and it’s implicit warning) being said, sauna-induced hyperthermia has been shown to induce a robust activation of the sympathetic nervous system and the hypothalamic-pituitary-adrenal (HPA) axis.

One study demonstrated that men that stayed in the sauna that was heated to 80°C (176°F) until subjective exhaustion increased norepinephrine by 310%, had a 10-fold increase in prolactin, and actually modestly decreased cortisol.1,15 Similarly, in another study, women that spent 20-minute sessions in a dry sauna twice a week had a 86% increase in norepinephrine and a 510% increase in prolactin after the session. 35

In addition to increasing norepinephrine, heat acclimation has actually been shown to increase biological capacity to store norepinephrine for later release. 38 In light of the fact that the norepinephrine response to exercise has been demonstrated to be blunted in children with ADHD and that norepinephrine reuptake inhibitors (NRI) are frequently prescribed to treat ADHD (among other things), use of heat stress and subsequent acclimation should be tested for it’s effectiveness as an interesting alternative therapeutic approach. 39

Neurogenesis

Heat stress has been shown to increase the expression of brain-derived neurotrophic factor (BDNF) more than exercise alone when used in conjunction with exercise. 40

This is important because BDNF increases the growth of new brain cells as well as the survival of existing neurons. An increase in neurogenesis is thought to be responsible for enhancing learning. 41 BDNF’s role in the brain is also to modulate neuronal plasticity and long-term memory, while also having been shown to ameliorate anxiety and depression from early-life stressful events. 42 In addition to the function BDNF plays in the brain when it’s released as a consequence of exercise, BDNF is also secreted by muscle where it plays a role in muscle repair and the growth of new muscle cells. 43

While BDNF has specifically been shown to play some role in relieving depression from stressful early-life events, whole-body hyperthermia has also been demonstrated to improve depression in cancer patients. 44 In this particular study, however, it was speculated that beta-endorphin (which is also induced by hyperthermia), not BDNF, may have been the agent responsible for this effect. As an aside, one of the reasons whole-body hyperthermia is sometimes used with cancer patients is because it can enhance the effects of chemotherapeutic agents. 45

The Runner’s High and The Role of Dynorphin

Ever wonder what is responsible for the “runner’s high” or post-exercise highs, in general? You’ve probably heard that it’s due to endorphins, but that’s not the whole story.

Beta-endorphins are endogenous (natural) opioids that are a part of the body’s natural painkiller system, known as the mu opioid system, which block pain messages from spreading from the body to the brain in a process called antinociception. What is lesser known is that the body also produces a peptide known as dynorphin (a “kappa opioid”), which is generally responsible for the sensation of dysphoria. The discomfort experienced during intense exercise, exposure to extreme heat (such as in a sauna), or eating spicy food (capsaicin) is due to the release of dynorphin. The release of dynorphin causes an upregulation and sensitization of mu opioid receptors, which interact with beta-endorphin. 46 This process is what underlies the “runner’s high” and is directly precipitated by the discomfort of physical exercise. Translation: the greater the discomfort experienced during your workout or sauna, the better the endorphin high will be afterward. Now you understand the underlying biological mechanism that explains this.

How is this relevant to hyperthermic conditioning and sauna use?

Heat stress from heat exposure in a dry sauna has been demonstrated to cause a potent increase in beta-endorphin levels, even more than exercise alone.1,15

A study in rats explains this somewhat: dynorphin delivered directly into a part of the hypothalamus in the brains of rats triggers a drop in their body temperature, while blocking dynorphin with an antagonist was shown to prevent this same response. Similarly, mu receptor agonists have been shown to induce increases in body temperature in rats. 47 What this seems to imply is that perhaps, by deliberately manipulating your body temperature you are actually directly engaging the mu (endorphin) and kappa opioid (dynorphin) systems since they clearly play a role in temperature regulation in general.

In Conclusion

To recap and drive the point home: acclimating your body to heat stress by intermittent whole-body hyperthermia via sauna use (“hyperthermic conditioning”) has been shown to:

Increases BDNF, which causes the growth of new brain cells, improves the ability for you to retain new information, and ameliorates certain types of depression and anxiety.

Causes a robust increase in dynorphin, which results in your body becoming more sensitive to the ensuing endorphins.

Life is stressful.

When you exercise, you are forcing your body to become more resilient to stress (somewhat paradoxically) through stress itself.

Hyperthermic conditioning is a novel and possibly effective tool that can improve your resistance to the sort of stress associated with fitness pursuits as well as some that are not traditionally associated with fitness such as the protective effects of HSPs on various types of stress. That being said, deliberately applied physical stress, whether heat stress or ordinary exercise, is something that requires caution.

You shouldn’t avoid it altogether, but you should use good common sense, not overwhelm yourself, and make sure to know your limits. (NOTE: you should not drink alcohol before or during sauna use as it increases the risk of death). 48 Personal variation probably comes into play when finding your own sweet spot for building thermal tolerance while avoiding over-extending yourself.

I believe that hyperthermic conditioning in general may be worth a closer look as a tool in the toolbox of athletes. Perhaps it can be used for much more than just relaxation?

If you are pregnant or have any medical condition, saunas are not for you. Speak with your doctor before starting this or any regimen involving physical stressors.

Be careful, ladies and gents.

###

ABOUT THE AUTHOR: Dr. Rhonda Patrick

You can find more video and writing from Dr. Rhonda Patrick at her website, FoundMyFitness.com.

Hannuksela, M. L. & Ellahham, S. Benefits and risks of sauna bathing. The American journal of medicine 110, 118-126 (2001). This is actually an important review article that covers some of the benefits of sauna use including the cardiovascular advantages and hormonal changes such as the boost in GH levels. I also like it because it covers some of the risks of alcohol use before or during the sauna.↩

Ricardo J. S. Costa, M. J. C., Jonathan P. Moore & Neil P. Walsh. Heat acclimation responses of an ultra-endurance running group preparing for hot desert-based competition. European Journal of Sport Science, 1-11 (2011). The sample sizes in both studies referenced here and in #4 have small sample sizes but they are two independent studies that compliment each other. This study also reinforces the endurance enhancements in #5.↩

King, D. S., Costill, D. L., Fink, W. J., Hargreaves, M. & Fielding, R. A. Muscle metabolism during exercise in the heat in unacclimatized and acclimatized humans. J Appl Physiol 59, 1350-1354 (1985). This study shows that glycogen utilization is decreased in runners after heat acclimation. The sample size is small but ref #7 (another small sample) is an independent study that shows the same effect.↩

Scoon, G. S., Hopkins, W. G., Mayhew, S. & Cotter, J. D. Effect of post-exercise sauna bathing on the endurance performance of competitive male runners. Journal of science and medicine in sport / Sports Medicine Australia 10, 259-262, doi:10.1016/j.jsams.2006.06.009 (2007). This study shows the effect of preconditioning the body to heat stress by using a sauna for at least 30 min directly after after training session. While the study sample is small, other studies referenced in #2, #5 reinforce and compliment this. I also have some anecdotal data. I did some serious experimentation with the sauna a couple of years ago when I had access to a sauna. I would sit in the sauna for up to 60 min. until I pushed myself to extreme physical discomfort about 4-5 times a week. I substantially (and I know this is just anecdote) increased my running PRs.↩

Michael N. Sawka, C. B. W., Kent B. Pandolf. Thermoregulatory Responses to Acute Exercise-Heat Stress and Heat Acclimation. Handbook of Physiology, Environmental Physiology (2011). This is a good review article that covers many of the mechanisms that underly the endurance enhancements as a consequence of heat acclimation.↩

Kirwan, J. P. et al. Substrate utilization in leg muscle of men after heat acclimation. J Appl Physiol (1985) 63, 31-35 (1987). The findings in this study reinforce the data in ref #3. Both small sample sizes but multiple studies showing the same effect makes the argument stronger.↩

Selsby, J. T. et al. Intermittent hyperthermia enhances skeletal muscle regrowth and attenuates oxidative damage following reloading. J Appl Physiol (1985) 102, 1702-1707, doi:10.1152/japplphysiol.00722.2006 (2007). This is an important paper because it shows that intermittent hyperthermia can enhance the regrowth of skeletal muscle in rats after disuse via induction of heat shock proteins. Having a quantitative way to non-invasively measure muscle mass in humans is difficult. Even though the experiment was done in rats (N=40) this is a good study because it also shows mechanism.↩

Kokura, S. et al. Whole body hyperthermia improves obesity-induced insulin resistance in diabetic mice. International journal of hyperthermia : the official journal of European Society for Hyperthermic Oncology, North American Hyperthermia Group 23, 259-265, doi:10.1080/02656730601176824 (2007). This study was done in mice (N=20) but it demonstrates a very important mechanistic finding that hyperthermia increases the expression of glucose transporters in skeletal muscle, thus improving insulin sensitivity. Exercise (which elevates core body temp.) is known to improve insulin sensitivity. This is a cool mechanism by which this can occur.↩

Yamada, P. M., Amorim, F. T., Moseley, P., Robergs, R. & Schneider, S. M. Effect of heat acclimation on heat shock protein 72 and interleukin-10 in humans. J Appl Physiol (1985) 103, 1196-1204, doi:10.1152/japplphysiol.00242.2007 (2007). This study includes a relatively small human sample size (N=12) but it is a very important because it demonstrates that heat acclimation causes a higher induction of heat shock proteins upon later exercise. This is the fundamental concept behind hyperthermic conditioning.↩

Moseley, P. L. Heat shock proteins and heat adaptation of the whole organism. J Appl Physiol (1985) 83, 1413-1417 (1997). This is a review article that explains some of the functions of HSPs and reinforces the data from reference #11 demonstrating that heat acclimation can increase the expression of HSPs.↩

Kuennen, M. et al. Thermotolerance and heat acclimation may share a common mechanism in humans. American journal of physiology. Regulatory, integrative and comparative physiology 301, R524-533, doi:10.1152/ajpregu.00039.2011 (2011). This study is another small human sample size (N=8) but it reinforces the data from ref #11 because it demonstrates that some of the positive effects of heat acclimation are due to increased expression of HSPs. The study even shows specificity here by administering an HSP inhibitor, which ameliorates the positive effects of heat acclimation.↩

Leppaluoto, J. et al. Endocrine effects of repeated sauna bathing. Acta physiologica Scandinavica 128, 467-470, doi:10.1111/j.1748-1716.1986.tb08000.x (1986). This is a very important study because it shows the profound hormonal responses to repeated sauna use in humans (N=17). By day 3, growth hormone increased 16-fold, highlighting the importance of hyperthermic conditioning.↩

Kukkonen-Harjula, K. et al. Haemodynamic and hormonal responses to heat exposure in a Finnish sauna bath. European journal of applied physiology and occupational physiology 58, 543-550 (1989). Even though the human sample size in this study is small (N=8), it shows that varying temperatures and durations differentially affect hormones. Small sample or not, the fundamental chemical changes in this study are reinforced from the data referenced in #1 and #4.↩

Ftaiti, F. et al. Effect of hyperthermia and physical activity on circulating growth hormone. Applied physiology, nutrition, and metabolism = Physiologie appliquee, nutrition et metabolisme 33, 880-887, doi:10.1139/H08-073 (2008). This study shows that hyperthermia SYNERGIZES with exercise to increase growth hormone levels in humans. So you can feel the burn from your routine and then jump immediately in the sauna for amplified effects. Again, small sample (N=8) but its conclusion is logical and intuitively follows the other studies. Anything that substantially increases core temperature should increase growth hormone and the effects should potentiate each other.↩

Nath, K. A. et al. Induction of heme oxygenase is a rapid, protective response in rhabdomyolysis in the rat. The Journal of clinical investigation 90, 267-270, doi:10.1172/JCI115847 (1992). This reference is relevant to the mechanism by which hyperthermic conditioning may protect against rhabdomyolysis: induction of HSP32.↩

Singh, R. et al. Anti-inflammatory heat shock protein 70 genes are positively associated with human survival. Current pharmaceutical design 16, 796-801 (2010). This study was a longitudinal cohort of a Denmark population (N=168) that found a slight increase in longevity (1 year) in females that had a polymorphism in the HSP70 gene that was associated with increased HSP expression upon heat stress.↩

Laatikainen, T., Salminen, K., Kohvakka, A. & Pettersson, J. Response of plasma endorphins, prolactin and catecholamines in women to intense heat in a sauna. European journal of applied physiology and occupational physiology 57, 98-102 (1988). This study reinforces ref #15 in terms of the norepinephrine response but this demonstrates it in women. Also, the smaple size is small (N=11), so it good to have multiple studies showing similar effects.↩

Narita, M. et al. Heterologous mu-opioid receptor adaptation by repeated stimulation of kappa-opioid receptor: up-regulation of G-protein activation and antinociception. Journal of neurochemistry 85, 1171-1179 (2003). This study was done in mice but shows that repeated activation of kappa opioid receptor causes mu opioid receptor to become more sensitive to beta-endorphin. This study provides a mechanism by which the dysphoric feeling from exercise or heat stress can ultimately result in a better “endorphin high.”↩

Heckmann, J. G., Rauch, C., Seidler, S., Dutsch, M. & Kasper, B. Sauna stroke syndrome. Journal of stroke and cerebrovascular diseases : the official journal of National Stroke Association 14, 138-139, doi:10.1016/j.jstrokecerebrovasdis.2005.01.006 (2005). This reference is only an N=1 where a a man had consumed several glasses of wine before he got in the sauna and was, subsequently, found dead. Alcohol consumption while in the sauna can cause severe dehydration, hypotension, arrhthymia, and embolic stroke. This is also reviewed in reference #1↩

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206 Replies to “Are Saunas the Next Big Performance-Enhancing "Drug"?”

Wonderful post and very informative. Recommend that the fraternity of experts have a roundtable on hyperthermic vs hypothermic conditioning. Tim’s podcast with Wim Hoth and references to Cold Therapy (Cold Thermogenesis) in the 4HB and made very strong hypothesis for it’s fat-loss, mood enhancement and muscle recovery qualities. For the fans, and citizen scientists out there (like myself), it’s going to be a challenge to determine how to properly incorporate this in a minimal effective dose style protocol. Curious as to what should we sacrifice in a full pareto style maximal hypertrophy protocol so as not to burn much more free time (eg. drugs/diet/exercise). For example, a 30 min workout for maximal hypertrophy, 30 min sauna, 10 min ice-bath (morning and night), 2-3 times a week might be flirting beyond the borders of the 4-hour-body mantra, especially if you combine the time tax for meal prep and constant eating. I’ll document some results during my experiment this month with Nate Green’s 28 day protocol for gaining 20 lbs. Thanks again for putting this together guys. – R

GREAT INFORMATION! The benefits are almost countless! I never thought heat could be so helpful, I’ve personally used this method when I get a cold. I’ll take my natural meds (mushroom supplements, fruit juices, etc) and go to the gym and run on the treadmill wearing a heavy warm-up suit. Obviously I get really hot and sweat a lot. I always looked at it as just a way to sweat more, and cycle the meds into the body, sweat out the bad stuff, and drink more fluids. It has always helped me get better faster vs just taking those meds and resting. Luckily I’m in Phoenix, AZ and we’ve got an endless supply of heat in the summer. Thank you! Great article!

I think its reasonable to stay home if you’re sick but advising a sick person away from the gym isn’t going to keep an otherwise healthy person from picking up a bug at the gym. Some flu like bugs are contracted through carriers that never show symptoms and others originate from lower organisms (mold and fungus in ventilation). I assume that’s why there is sanitation requirements (like bottle sprays and wipes) in public facilities and health codes for insured gyms. If you’re getting sick from going to the community gym, and still have an interest in being a part of such a fraternity, then perhaps you should look at it as an opportunity to improve your immune response rather than preventing interaction. Cold thermogenesis might be a start. Excelsior!

Tim, awesome article, and thanks for the retweet (phone currently on silence as it gets blown up from all the twitter notifications…)

Question– I’ve read the benefits of cold showers as well. And you’ve obviously been a fan of ice baths as mentioned in past posts. Is there anything special you would take into consideration to take advantage of both? Timing? Frequency?

Sorry, but this makes no sense. As someone stated earlier (or technically later now…), why would one want to shock the system with a very cold response? This would simply decrease that amount of metabolic adaptations one could have acquired from the sauna (heat shock session), due to your decreasing mitochondrial biogenesis and activity by slowing the system (with temperature decreasing).

Thus, your claim on this seems off.

Curious to why you state, “cold shock immediately after sauna may be best…”

Very interesting post Dr. Patrick. I found the 3.5 increase in RBC count especially intriguing as an altitude training researcher and coach. For one, that type of hematological gain is equivalent to response some athletes see after spending 4 weeks at high altitude! Also, many of the top athletes who coach at altitude recommend running in sweats and/or sauna time towards the end of stints at altitude to help prepare the body for the more hot humid competitive environment at sea-level. It seems the benefits likely go beyond that, especially considering the proposed mechanism of RBC production increasing in response to higher blood volume. For example, when an athlete begins a stint at altitude EPO production typically begins to decline back to baseline after the first week. This initial period of time at altitude is also associated with hemoconcentration, the opposite response to that of heat acclimation. I wander if mixing heat exposure after this first week could help extend the duration of the initial EPO spike and maximize gains in red blood cell production. If so it would definitely be synergistic with altitude training, but, as Tim mentioned, precautions regarding exposing the body to that extra stress would have to be taken especially considering the stress altitude and training place on the body. Great post and keep up the good work with Found My Fitness.

Interesting insight. It could be synergistic or it could go the other way! Stress induces a hormetic response by inducing the expression of genes that help you cope with stress, so you reap the benefits of the stress response. However, stress + stress can induce the opposite effect, the toxic response! When your cells are already stressed and you add more stress, this can push them over the edge—pop!

I’m from Phoenix, Arizona, so I can tell you all about heat. It’s funny how people who aren’t from Phoenix start complaining when it hits 90 degrees–I’m not a long distance runner anymore but I can tell you that once you’ve gone running a few miles at about 110 degrees everything else seems like a joke. Interesting about the growth hormone, though. I’m going to see if I can get into a sauna here in Spain.

Most of the benefits for the dry sauna hold true for humid sauna as well. In one study, humid sauna actually caused a slightly more robust increase in GH compared to dry sauna. Most of the studies were done using dry sauna, which is why dry sauna is mentioned. Other means of elevating core body temperature may also apply, but they must be able to elevate it to a point of physical discomfort (ie. sitting in a hot bath for 30 min. would not compare to sitting in 176 degree F sauna for 30 min.).

Dr. Rhonda- I love your research and videos that you have made regarding heat acclimation. I have an infrared sauna and get in it very frequently. I run my infrared at 140 degrees and I sweat like I have never sweated before. I feel that my body is functioning at a better and higher level than prior to my sauna sessions. I have been very faithful at using my sauna for 4 months now. Infrared saunas heat the body from the inside out vs. from the outside in. What is your opinion regarding your research as it would relate to the infrared heat?

Quite intresting post, indeed. However, as I was reading trough the article, a couple of questions popped up in my mind.

1) First off; about the 1600% percent increase in HGH levels. Would it be reasonable to believe that the sauna is not the sole reason, but a factor in the equation?

-The sauna forces you to relax and take time off. HGH peak at night when you are at sleep, and simply taking a nap / siesta during the day will thus boost your HGH levels. Is the studies showing the 1600% increase comparing a group of working individuals to a group that uses 2 hours a day to relax, or are they comparing a group using the sauna to another group just taking 2 hours off? I would be even more intrested if the latter was the case; or if such a study could be performed.

2) When would be the ideal time(ideal regarding HGH boost and hypertrophy) to implement a sauna session in your schedule; taking into concideration the circadian rythm and other environmental factors?

The sauna feels relaxing afterwards (mostly due to the massive beta endorphin release) but, in fact, the sauna itself causes stress (in the form of heat stress) on the body. The 16-fold increase in GH was over baseline, meaning everyone was their own control. A couple of studies imply that a sauna session post-workout would achieve the maximum benefits.

I experimented with this for several years during collegiate track and field. I just did it because the heat helped me to become more flexible. Its funny because I would drink warm water to keep my body temperature from dropping, Not that I really could give you a good reason for that. I had awesome gains in strength and endurance. I never looked further into it but after reading this its very evident that I was unknowingly “hypodermic conditioning” myself and it helped with increases in performance.

If you feel to hot, you probably are. Take a break. Also, make sure you drink a TON of water. Very important.

Steam rooms would elevate core body temperature but because the steam is coming into contact with your skin, you mostly likely can’t sit in a 176 degree F steam room for 30 min. Since many of the effects (GH release, HSP induction etc) in these studies required an amount of heat stress that was generally uncomfortable… you would likely achieve some of the benefits, they may not be as robust. Of course, these are just my thoughts, no evidence of that yet.

Fascinating post! I’ve been using an infrared sauna in my home for two years, on average 30 minutes 4+ times a week. I had never liked saunas before trying infrared sauna and only learned about IR saunas because I was recommended them by parents who had used them with their autistic children (I work with kids with autism in San Francisco). I tried one once and immediately researched and purchased one for myself.

As a former professional dancer and gymnast I’ve found huge benefit! I sweat extremely easily from using the sauna so regularly, which results in me dancing better, and found post-sauna to be an optimal time to stretch. I’ve found that heating regularly has taught me how to let go of physical tension outside of the sauna. I am able to relax physically more now during performance than I ever was before. I’ve experimented like crazy to find how long pre- or post- workout I like to sauna, at what heat, and for how long. (Not too late at night on it effects sleep, ideally with an hour or two after exercise or more than two hours before exercise, between 110-130 degrees for 20-30 minutes).

I’ve also found a lot of ancillary benefits to having an sauna. First off, because I sweat so regularly I am forced to drink much more water. Like most people, I’ve always been a bit dehydrated. No more. I started drinking Limeaide (yuck!) when I found myself hugely thirsty in the first months after buying my sauna. Then I moved over to a lot of water and a lot of Gatorade. I’m never dehydrated anymore.

Another fun aspect of having my sauna is that no one has a sauna in their house – especially in San Francisco! It has become a way that people recognize me or my house. I have hosted business meeting in my sauna, read books that I’d never get to otherwise (like on an airplane – no distractions!) and it has been an amusing, unexpected thing to ask dates (“want to try the sauna?”)!

My background is in the science of motor learning, thus the connect between my career in dance and my work with kids with autism. Prior to this post I had never read in the literature about sauna as performance enhancement. I just know that it works for me! Really appreciate your in depth look!

A couple of questions:

What’s out there on IR sauna versus regular sauna? I experience a BIG difference but haven’t seen much outside of propaganda.

To be honest I have not combed the scientific literature comparing the effects of FIR vs dry sauna yet… would be interested (and surprised ) to see if there is any good science comparing the two. The mechanisms that I refer to in this post really have to do with heat stress and the hormetic responses to it (such as hsp induction and GH release) and adaptations that occur (such as increased blood flow to many tissues upon later elevations in core body temp.).

I am not aware of any literature on heat stress and autism but I just published a paper last Feb. on a mechanism that I found by which vitamin D increases serotonin and oxytocin, both of which are important for prosocial behavior. I recommend getting vitamin D levels tested, most of US pop. has inadequate levels, including autistics.

How have they not been able to fix the underlying causes of autism yet? I have a friend with low grade autism, and his fatty acids were way off (on the extreme low side). He is still awaiting his casomorphin and gliadorphin tests. I am excited to see if he can overcome autism through nutrition and targeted supplementation.

A psychologist recently told him he would only be able to do menial jobs in his life, and he was really upset about that.

And also his vitamin D was 25 ng/ml. He (and I) have/had taurine deficiencies, so that would prevent the uptake of vitamin D due to poor bile production. After 2 months of supplementation it only went up to 30 ng/ml. He will hopefully begin taurine supplementation soon.

Very interesting research and findings! Would be interested in more specifics around exact temperatures and durations. Is hotter and longer necessarily better, or do results start to cap off after a certain temperature/duration? Sounds like it would make great material for the next edition of 4HB (also interested in material about improving flexibility, if you can squeeze that in there).

These are great questions. In some of the human studies, increased temperature and longer duration (compare 20-minute to 1-hour) had more profound endocrine effects and sympathetic activation (ie. norepinephrine release). The results do start to cap off after an extreme point. For example, 1-hour sauna sessions back-to-back (30 min. cooling period in between) for seven days in a row, will results in a plateau in these effects after day 3. First of all, this amount of heat stress is CRAZY and NOT recommended. Most likely this kind of extreme heat stress in such a short period of time does not give your body enough time to recover, so you are depleted of some of the precursors and the signaling pathways are stressed out! My personal anecdote: I noted the best results when I did a 45-minute sauna session 3-4 times a week post workout. My running PR was best and I also maintained lean muscle mass better than just workout alone. Of course, I would not do an extreme sauna session after an intense workout, that would be too much stress.

My grandfather runs 3 times a week (Tues-Thurs-Sun for 90-120 minutes) and takes exercise classes 3 times a week (Mon-Wed-Fri). Regardless of the weather — freezing rain, blizzard, -30°C or +30°C — he’s been stubbornly consistent with this routine for decades.

After each training session he goes to the steam room at the health club, pushes the button inside the steam room that activates the steam jets about 7 times in order to bring the temperature up to a scalding 120°F (“Make it HOT!”), and sits in the “schvitz” for an terribly long time. Wash, rinse, repeat.

It could be that the benefits of prolonged heat exposure mentioned above are contributing to his longevity (along with good genetics, quality of life, …).

I once tried dry sauna at the gym and I hated it. It was stressful, it takes time to relax. I was alone and the employee did not explain much, which can have contributed to the poor experience. After reading this I think I will try it again if I have the opportunity.

GH mediated IGF-1 increases lean muscle mass and reduces adiposity. Since sauna use causes a robust increase in GH, then I would assume that it would also speed up weight loss via IGF-1 mechanisms. I have not seen any good data directly testing the effect of sauna on weight loss yet but I will wave my hands on this one and say “yes.”

I think it is worth some experimentation. Preliminary data suggests that it does improve insulin sensitivity by increasing GLUT 4 transporters and thus glucose uptake into muscle cells. I would LOVE to see more research on this!

I’ve seen an interesting study where ice-bath after the sauna had interesting neuroendocrine effects, particularly on the locus coeruleus. It caused a massive release in norepinephrine, which helps with focus and attention.

I injured myself at a gym over ten years ago. Took me about ten minutes to get off a hack squat machine. The supposedly qualified assistants told me to take a sauna to ease the pain. Sure i could walk a little better afterwards. Then woke up in the morning locked shut and incapable of moving and almost screaming my head off. Phoned a doctor who laughed at me in a nice way saying ‘I bet you wished you hadn’t gone in that sauna because your blood congealed around the injury to protect you, then the heat melted the blood causing further injury now you could move’

Thanks for more cutting edge info. I enjoy Bikram yoga 2 to 3 times per week, this is a series of postured performed over 90 minutes in 110 degree heat. I sweat a great deal and feel awesome afterwards. Any reliable research out there on hot yoga and what are your thoughts on relative benefits related to this research?

I have not seen any solid studies on hot yoga having these particular benefits but I think that the the elevated temp. in combination with exercise would induce a significant heat stress that may be generalizable to hot yoga.

I’m a little concerned about the increase in prolactin – my wife suffered from depression for years which was eventually found to be related to excessive prolactin caused by a pituitary adenoma, and it looks like in general an excess of prolactin may be as bad as deficiency. Studies have even found a correlation with anger and hostility (http://www.ncbi.nlm.nih.gov/pubmed/6483849). So would a 510% increase put someone in the danger zone?

Interesting. My thoughts are a pituitary adenoma would cause a consistent and chronic elevation in prolactin (not to mention other aberrant elevations in endocrine hormones). This is very different from the acute effects of heat stress on prolactin, which do not persist for more than 2 hours. There are important feedback loops when it comes to the HPA axis, a pituitary adenoma causes disruptions in these feedback loops resulting in many other downstream negative effects. This is not the case with heat stress which results in acute elevations in prolactin.

1. Due to excessive sweating, increasing use of trace minerals and potassium is imperative.

2. “Wet” heat is FAR superior to “dry” heat (sauna).

3. Saunas are very draining in general. If a person is already deficient, this will further exacerbate symptoms of deficiency. Saunas are not designed for everyone – they are designed for those who lean toward excess (hyperactivity, insomnia, excessive sweating even when it is not hot, nervousness and red eyes are just a sampling of excess-based symptoms).

It’s probably somewhat generalizable to hot tub, which is why I’m using the term “hyperthermic conditioning” throughout the article. However, the specifics of the studies often do talk about saunas, specifically. Hot tubs, baths, etc. do have slightly different characteristics. You couldn’t sit in a 170 degree (fahrenheit) hot tub, for example. If you’re looking to achieve this effect, though, it’s probably better than nothing.

I wonder though because sitting in hot water should change your body core temperature much faster than dry heat (~25 times faster). There may be an equivalent effect overall with the hot tub temperature water ~104 degrees.

Holy crap! N of 6?? That is a tiny, pilot study. That’s exciting that the finding are corroborated by another study also with a small sample size, but much more work needs to be done to determine if there are other factors involved. Did any of the participants’ characteristics influence the results? What about environmental conditions? Their diets?? You really can’t tell with those small numbers.

The assumptions of hyperthermic conditioning and adaptation/endurance seem very intuitive and really interesting. I’d like to see this get more attention and encourage investigators to design larger studies to test what else may be impacting these huge results. The implications for injury healing, ADHD, and increasing diabetic insulin sensitivity are incredible!

Tim or Dr. Patrick- have you heard of any bigger studies underway??

I’m curious about inflammatory responses and would love to know more about the impact on cortisol levels and the evolutionary reasons for this biological design. I look forward to reading the articles!

Terrific article. I waited over two years to get a double hernia operation here in Canada, and couldn’t train the way I was accustomed to. After a bit of research, I purchased an infrared sauna, and used it regularly. I felt terrific afterwards, and this helped with the mild depression I was experiencing due to my physical inactivity, and the fat that had accumulated around my midsection. Post surgery, I had my six-pack back in less than 6 months, due in part to 4hbody, and sauna use. Thanks for the great info… haven’t used my sauna in months, and it is now up to temperature. Time to grab a towel.

The effects of the sauna on the dynorphin/endorphin opioid system can explain some of anti-depressant effects. Sauna induces dynorphin, that dysphoric feeling when you are in heat stress. Activation of the kappa opioid receptors by dynorphin, while dysphoric, causes an upregulation of the mu opioid receptors and sensitization to beta endorphin. The long-term effect of this will be massive sensitivity to to a much smaller amount of endorphin—translation: anti-depressant.

*Resetting biorhythm, in order to wake up earlier. Nothing else worked for me.

*Stimulating a sense of urgency. This is related to different stress-hormones that are produced in response to the radiation. The effect is very significant, and my productivity shoots through the roof.

Why? Because it makes my objectives feel more urgent.

The sense of urgency occurs not just acutely, but it stays for days after the exposure.

*Decreasing fat-gain on cheat days. The radiation seems to enhance glucose tolerance, due to different interleukins, among other things. Studies also indicate that it inhibits adipo- and lipogenesis.

*Stimulating Melanogenesis, of course. (The tanning response, which works just like building muscle: stimulation -> protein- and hormone synthesis.)

*Hormonal manipulation. It seems to enhance libido and many other factors related to hormones. I haven’t measured if it actually raises my T-levels, but it sure does feel like it.

As melanogenesis is a process of Protein synthesis, and the stimulation is cAMP-mediated, this seems like a valid hypothesis. Although, until measured, it’s just a guess…

*The minimal effective dose was used in all sessions, to minimize risk.

My dose was 4-6 minutes, with forskolin (4 mg) taken prior to sessions.

I have also used Forskolin and PDE-inhibitors prior to sessions to maximize the effect of the sessions (through cAMP mediated mechanisms).

Disclaimer: I’m aware of the dangers associated with sunbeds. None of this was intended to be used long-term. The sole purpose of the experiments was to learn and find out new things.

For example – I’m very eager to try these experiments on my next vacation, when I have access to nature’s own, less carcinogenic souce of UV-radiation. Sunshine!

If you don’t have access to a sauna in “practical proximity”, can you induce heat stress physically in a “controlled fashion”? For example, can you have some sort of heat probe (like a heart meter) and do burpees for 30 min that will overheat your body consistently for that period? Or is this too complex or problematic?

I’m curious Dr. Patrick if you compared the dry-heat of a sauna (as you indicate around 160F-170F with very low humidity) in this study to the wet-heat of a steam room that would be around 104F-109F with 100% humidity, and if wet-heat has the same corresponding benefits in your test subjects.

I have not seen any studies directly comparing the dry sauna with steam room. However, the steam room would likely also induce a heat stress that would also activate the heat stress response in the body (ie. hsp’s and GH). In my mind, the difference may be in the robustness in the activation of these heat stress response mechanisms.

However, you don’t mention if long term exposure to heat stress has any negative effects on the body. Could you describe some of the possible unfavorable outcomes, i.e. decreased testosterone output or lower sperm production in men.

While I do think you’ve provided valuable arguments for experimenting with heat shock, people should be aware of any undesirable effects that might be cause concern and so they more information to make a better decision before embarking on heat stress sessions.

Rhonda, Tim, or anyone else have experience or research for when it would be best to do a post-workout meal or smoothie when also planning on doing a post-workout sauna? 4HB and others have stressed the importance of eating protein within 30 min of resistance training.

I will probably try slamming a protein smoothie, going into the dry sauna, and hoping I don’t puke :(.

My question has to do with hot yoga. Much of your article has the heat conditioning in a sauna after the workout. What about during as in the case with hot yoga? Are the results you discussed compromised because of training? Is the relaxation post workout part of the reason for the results? Or do you simply need to spend the time in the heat?

As a Finn who has been using saunas from a very young age as a natural part of my daily life I can’t help but feel a bit strange when the sauna is discussed in such a scientific way. For those who don’t know, the sauna has deep roots in Finnish culture as a place for relaxation as well as socializing. It has been said that some of the most important political decisions in Finland have been made in the sauna.

Personally, I have never used the sauna as a “performance-enhancing drug.” It has simply been something that is a central part of our culture and that I very much enjoy. All other benefits are secondary to me.

I am definitely not against using saunas in order to make biological gains but I would like to encourage people to also start seeing the sauna as a source of enjoyment and perhaps mental well-being, instead of just focusing on improvement in performance.

What seems to be missed is this data was from a traditional sauna, now they have the Infrared sauna’s, this is the type I have which mine only heats up to 140 degrees F. It would be interesting to see the data provided by the different types of sauna as the infrared heat is apparently supposed to go deep into the muscle where the traditional sauna doesn’t ? And seriously 212 degrees for 1 hour in a regular sauna you might die…that seems extremely extreme, Doing an hour in my infrared at 140 is hard, like after 40 minutes ever additional minute seems like 10 minutes. FYI, I purchased it because I don’t want to do cardio, and they claim it burns up to 600 cals an hour…I have no idea if it is true or not.

I think following the 4 Hour Body diet plan gave me diabetes. I have been a vegetarian for 20 years and gained weight during a time of depression. I was so happy to have found Tim’s book and followed the diet precisely, which made me loose 70 pounds! Problem is that the only vegetarian protein on the list of acceptable foods is eggs… and new research shows a link between eating eggs and developing type 2 diabetes. Even one egg a day increases the risk… and I was eating 11 eggs per day while on the 4 Hour Body plan.

It’s kind of off-topic, but your question is important, so I hope Tim and Rhonda will forgive me for addressing it here.

The first question is: When you say the slow-carb diet may have given you diabetes, do you mean that you have diabetes and think that eating lots of eggs may be the cause, or that you are eating lots of eggs and worried that you may have diabetes?

The second question is: What does your doctor say?

I had a look at the scientific/slash medical literature on eggs and diabetes. (Disclaimer: I’m not a doctor, but I’m a specialist in academic writing, so trawling through medical journals is no sweat.) Interestingly, studies show a significant correlation between regular egg consumption and type 2 diabetes (a meta-analysis is at http://ajcn.nutrition.org/content/98/1/146.full) but nobody knows why. A popular explanation is increased dietary cholesterol, though the meta-analysis says “However, RCTs in participants consuming a carbohydrate-restricted diet showed that consumption of 3 eggs/d for 12 wk did not significantly change plasma fasting glucose (72, 73) and insulin resistance (73) compared with placebo (equivalent amount of egg substitute without dietary cholesterol).”

As for the slow-carb diet, there is plenty of vegetarian-compatible protein other than whole eggs. Egg whites are recommended and would probably not have the same effect as whole eggs, especially if the cholesterol theory is correct. Beans, which make up a massive part of a slow-carb diet, are a good source of protein, especially when combined with nuts (which can be consumed in moderation). Cottage cheese is also allowed. See the appendix “The Meatless Machine” for details on vegetarian slow-carb.

Outside the published research, have a look at body-builders. They often consume ludicrous amounts of eggs, but don’t seem to be more prone to type 2 diabetes than the general population (possibly because of the beneficial effects of resistance training on insulin, but that’s another story).

My dad goes to the Sauna up to 5 times a week for more then 30 years now and I always wondered why.

After trying i can say its just great. Apart from the apparent effects you describe here, I can only say a hard sauna session is the most relaxing thing there is. It really does feel like you just took a 60 minute run – gets you totally relaxed.

Tim, Your blog email signup service is not working. It says I’m already subscribed but I never get any posts. You may be losing thousands/?millions? of people who are wanting to grow in the 4 hour ways.

Very interested in trying this out. I only have a question about the ‘sauna sessions’. The article says 20 minute and 30 minute sauna sessions. Does that mean 20, 30 minutes without going out or can you also do 10 minutes, go out for a minute and then 10 minutes and so on.

I can gather from The information that ot might be better using the sauna at different times in relation to the workout, depending on what your aim with the workout is. For instance, is it better to go to the gym AFTER the sauna (if it’s hypertrophy that you’re after), considering the sentence “repeated exposure to whole-body, intermittent hyperthermia (hyperthermic conditioning) through sauna use has an even more profound effect on boosting growth hormone immediately afterward”? Is it better to run BEFORE the sauna, considering the study where the participants increased their running until exhaustion by 32%?

What I mean here is the differences between PRE-workout sauna=increased GH-levels and POST-workout sauna=increased endurance.

Hey Rhonda, So it is beneficial to do a heat session after a workout where the goal is muscle hypertrophy increase (MHI)? And i know you have to cool down real quick afterwards, but taking a prolonged ice bath afterwards will not be beneficial for the cause? Because it is not linked positively to MHI

I play soccer as well, which is not optimal for MHI, because of the energy surplus requirements, but if i want to take ice showers anyway in the week i could best do this after a soccer session? Because my goal of those workouts are not MHi anyway , my goal afterwards is to reduce stress as much as possible to not interfere with my weight sessions the coming days.

This is great. I’ve heard Dan Gable and some other Olympic wrestlers speak about the benefits of heat before and this drives it come with a lot of great science and references to back it up, thank you.

Is it possible that the increased IGF-1 and hGH would provide bone / ligament healing advantages? It seems you mentioned primarily muscle, but I’ve recently gotten a broken ankle. Would love to hear your thoughts!

1. Saunas are referred to “dry saunas” throughout this post. Are the effects from “wet” or “steam saunas” similar, or does dry heat have a particular advantage?

2. What role does cold therapy or contrast therapy play in your opinion? Tim has put out some great information with regards to cold therapy and fat loss. Does this mitigate the effects of heat therapy or can the two be used together for different means?

This is quite an informative article! I love that you do guest posts on your site, even if you get affiliate fees, you are still spreading good info. I’m curious to know if you are going to post a follow up article about this subject? Some people argue that when you are reading, and you don’t understand all of the words, your absorption of the material is inhibited. So if you post a follow up article, it might be easier to understand everything completely =).

It seems like saunas are now found at a lot of the newer apartments in the Bay Area so maybe they will popularize. I’m sure after you’ve posted this article there will be thousands of people trying it in some form.

I admire all of the biohacks you try and share with everyone. I am a tinkerer as well but my health has declined after serving in the military. I would love to find something that works for me personally. At the moment I have a bad reaction to even taking a bath that is too hot (racing, pounding heart, dizzy, ect). So it wouldn’t be smart for me to try using a sauna at the moment. I have been slowly losing the strength in my lower legs due to inactivity from adrenal exhaustion. For now at the most I can try to walk 3 miles but even that is a lot.

Anyways, thanks for sharing info on how to improve and I hope to apply this method when I get healthier. You’re awesome!

Hola! I am an avid Bikram practitioner. Recently, I underwent a couple of minor dermatologic surgeries and was told not to attend hot yoga for a couple of weeks. I knew my body would start to ache but was truly startled about the effect on my mood, which plummeted so deeply that I found myself in tears for no reason whatsoever. I am absolutely an advocate of demanding exercise and I love reading that I fanaticism has solid scientific roots. I’m also happy that my mood shift has a rational explanation other than, “Suzie, you’re nuts” 🙂

Rhonda – Great, thorough piece. I’m curious about the therapeutic difference between the traditional hot-rock dry sauna and the more recent (and less expensive) “infrared” (far/near/carbon/etc) varieties. The infrared ones don’t get nearly as hot, but they claim to focus the radiant energy a couple of inches below the skin’s surface, so the surrounding air doesn’t need nearly as much heating. Is that bogus or legit? Does hyperthermic conditioning prefer one to the other?

This is a pretty impressive assemblage of information, and that there are benefits seem clear, but as I read through it all, I kept thinking: What about us guys? There have been tons of studies that show heat not only compromises sperm quantity and quality (Tim even talks about this in the 4HC. And a dip of the jewels in hot water was even 19th century contraception, apparently, and conception rates are demonstrably lower in hot months), as well as actually increasing testosterone, which would seem to complicate a lot of the benefits here. Would love to hear any thoughts on this, as I know quite a few guys struggling with infertility/varicoceles, and this great post would seem to be a lot riskier for them. Thanks!

I also find this to be a concern…and I was quite influenced by Tim’s ice bath section in his book. I’ve seen quite a bit of impact in my performance through ice baths and weight loss through “shivering” off the fat. I wonder how the prolonged exposure to heat affects testosterone here. I’ve actually avoided prolonged heat exposure for this reason unless I’ve felt I just needed to increase my circulation a bit. I’ve heard that just taking a 30 minute hot shower 5 times a week can have profound impacts on sperm count/quality and testosterone. Maybe the heavy exercise here helps counteract that, I am not sure. In conjunction with heavy exercise maybe this is what induces the “hyper-hyper-trophy.” But I just wish she was a little more clear on that.

It doesn’t help that it’s a girl talking about this either. Us guys I think would like to see a nice, healthy, fit strong man say that he does all of this sauna therapy without any impact on his manliness. If anyone wants to discuss this more, I’d be happy to find some more concrete evidence on how heat can hyper-extend the muscles aside from decreases in testosterone. So I’m assuming this is not pre-workout advice…more post-workout recovery related.

Interesting thoughts, Luke. I doubt we’re going to get a response in here at this point, but it would be interesting to see more on the overall effects of heat beyond the narrower focus of the benefits cited in this experience (there’s a book in “hot & cold”!). It seems logical that “performance” gained out at the extremes has a real potential of reducing, over time, a broader definition of “performance”. Lots of interesting studies on the detrimental effects of heat on the testes here: http://scholar.google.com/scholar?hl=en&q=%22scrotal+cooling%22+&btnG=&as_sdt=1%2C5&as_sdtp=

Really curious about this, and fascinated by the science, but it makes me wonder whether it’s literally playing with fire.

Great article. Seeing the scientific facts associated with a cause might be at the risk of one person (Tim as the subject matter), but provides a clear indication of the benefits and risks in a comprehensive manner. I have incredibly low blood pressure, which sometimes creates a fainting scenario..so i have to be diligent about my use in saunas. Although, we have a space dedicated to a sauna, we have been contemplating the use of a steam room instead. Comparatively, heat sources are different which can affect the optimal heat range and the effects. Which would you suggest to have the most optimal health benefits.

The IGF-1 increases related to shortened life spans in the non-humn data may well not be relevant. The problem in almost every study, the human ones included, is that the levels of IGF-1 are rarely stated. IGF-1 is released following Growth Hormone (hGH) spurts and there is a nocturnal burst, an early morning burst on rising gherkin levels and bursts that occur from large muscle mass activity.

This contrasts to the states induced by genetic manipulation, or is chronic disease states when IGF-1 may be triggered by other factors that affect its production in the liver. These would NOT be normal healthy responses and so, different clinical outcomes could be expected from those where hGH is released due to normal body stimuli. AND, this can apply, too, to people injecting hGH in NORMAL physiological doses.

hGH is an amazing hormone, carrying with it the AOD fragment that current studies show is a potent fat burner with NO IGF-1 activity. Tell that to the idiots at WADA.

I setup my small bathroom with far infrared units made for a built in sauna for my chronic pain/depression. I’ve tried many different therapies & this is one of the few that has a big impact on my ability to function.

I do enjoy going into a Sauna, it tends to instantly relax me as I listen to my music or a podcast. The one drawback I have found is you can have an empty sauna and the one guy that comes in has to sit right next to you…it’s sweaty enough in there:) It also gives you time to think about things.

I know Tim hates the term ‘genius’; so lets just call him ‘special’. He’s our ‘special’ little friend.

Given this information, it isn’t totally unfeasible that Tim’s ‘special’ness isn’t at least a little bit contributed to his enduring this heat testing.

I mean…it’s at least a considerable variable right?

If we are looking for variants outside of the mean, it’s a fair comment to say that our mate here is one of those rakkin frakkin darn variants.

We don’t want to attribute his ‘special’ness to just Tim himself; because it’s impossible to replicate a person (well…probably not impossible. Just really frigging hard at this point in time).

If Tim is one of Buffets Advanced Coin Flipping Orangutans, what made him so? Given the above information; I’d say a lifetime of sensitivity to overheating (despite him bitching about it) could have been a significant variable.

I had something similar; I had pretty vicious plantar fasciitis as a kid. From about 8-9; and 12-13; I had to walk around on my tiptoes like a fairy.. Okay, maybe I didn’t have to; but it hurt, and I’m a big pansy when it comes to owies.

Low an behold, after a couple years of people making fun of the way I walk; my calves and glutes were so strong I had a 40 inch vertical; and won basketball scholarships overseas.

Maybe Tim’s sensitivity to heat stress contributed to him being outside the mean, and providing us with all this cool content and methodology.

The article said, “Skeletal muscle cells do contain stem cells that are able to increase the number of muscle cells.”

It is NOT the case that stem cells are CONTAINED IN other skeletal muscle cells. Rather, it is the general muscle TISSUES that contain these stem cells (or “satellite cells”) along with actual “muscle cells”. (In this use of terms, “muscle cell” means a cell that has developed to perform muscle contraction functionality. On the other hand, “stem cells” have not developed to perform a specialized function: they are available to be recruited for development into a specialized cell if the body decides to recruit them for a purpose.) The recruitment of these “satellite cells” in the creation of new “muscle cells” is one means among several through which hypertrophy can occur.

One basis for many fallacies (or, more bluntly, much BS) on the topic of bodybuilding is the failure to understand that there are a variety of biological processes that can cause a muscle to get bigger. They have different effects (e.g., increasing maximum available force for three seconds versus how long a lower force can be exerted continuously versus mere size without much functional effect) and they are triggered by different causes (e.g. number of reps, % of maximum, number of sets, frequency of workouts, length of workouts, etc.)

Very interesting article! I wondered about infrared saunas or steam rooms and if they might have a similar effect. I can access both of these at the gym but unfortunately they don’t have a traditional dry heat sauna.

Awesomely informative piece, and while I learned alot, I can’t say I was the least bit surprised. I first decided to try out the sauna on a regular basis after reading a chapter in a book on bodybuilding by Dr. Fred Hatfield (“Dr. Squat”) Touting it’s benefits. While I stuck with it for quite a while and it never turned me into Mr. Olympia overnight, I kept on doing it simply because I felt so doggoned good afterwards. A few years sown the road, however, the sauna just became inconvenient with my hectic schedule so I gave it up. While Im not alone in getting Strep Throat really bad once, sometimes twice a year and suffering heavily from it, one year the Strep spread into my blood stream, giving me Septicemia and damn near killing me. The following fall, I felt Strep coming on again . I was just barely getting back on my feet from the last bout with it, and I couldn’t afford to go through with it again. Then a single quote from the Hatfield book popped back into my head: “If I can get a man to sweat, I can cure him.” The Author of that little quote was Hippocrates, AKA: The Father of Modern Medicine. Without any real idea of the outcome, I hydrated adequately and grabbed an additional gallon of water. I weighed myself before I went in the sauna, and drank the entire gallon of water. I sat in the sauna taking quick breaks every 20-30 minutes until I had returned to the weight I was before I drank all the water, so basically, I sweat out the whole gallon of water. Bam. Felt 100% better. To this day, no matter how under the weather I feel, I can go to the sauna, drink a load of water, sweat it all out, and pretty much be completely healed.

You should be honored Tim or Rhonda because Mercola just made an article with the exact same title as yours and he linked Rhonda’s video in it, it also happens to be first place on google serps and first place in most popular articles on his website at the moment.

What would be the ideal practical application? Going to the sauna (up to 3 rounds) after a workout adds enormous stress on the nervous system. It seems like one has to have an enormous quality of sleep and off time to stick to that idea. It didnt work out for me.

Not sure what to say on all those points… Just wanted to mention that drastic stresses to the nervous system aren’t necessarily a bad thing – they can be the mechanism for triggering physiological responses mentioned in this article. Especially for exposure to hot and cold. Hence the efficacy of practices such as the Wim Hoff method. Personally, I have had very noticeable benefits from prolonged sauna use, and it’s provided significant relief to some chronic health issues I deal with, for up to 2 weeks after. But it hasn’t been in combination with any sort of workout.

Great research and article, and thanks for taking the time to respond to all the comments. I tried working through all the comments, but couldn’t read all of it, so I hope I’m not asking something already covered there.

As an elite endurance athlete, I can see and want to exploit the benefits of hyperthermic conditioning, but what is not clear for me is the macro-cycle timing or periodization and “volume” as pertains to hyperthermic conditioning, which is in effect “training”. Since my year is divided into off-season and the competitive season, is it safe to train this way during the competitive season, and to what degree? How long do the effects last, do you need to maintain them etc. I guess these are similar considerations to altitude training, which wears off after a while. I’m assuming the HGH effects last, but not the cardiovascular.

Saunas are not ‘traditionally used for relaxation’ as stated in the video. Most cultures in ancient Europe and North America used sweat lodges for health reasons, and the practice continues in Eastern European countries and Native American tribes today. In Ireland sweat lodges were widely used until the 1800s, and the practice involved locking a sick person inside the lodge using a stone slab and waiting 5 hours before they were let out; health was the primary reason, not relaxation. They all believed that it helped the body purify itself and fight illness. While they didn’t have the scientific basis discussed here, they intuitively knew that it was good for you.

Interesting to read this. For five straight years I’ve done steam bathing every single day for as long as I can bare it. I’ve experienced all sorts of profound benefits from this, but friends never believed me. They just assumed I was naturally intense and pumped. They’ve even accused me of using gear in the past although I’ve never touched the stuff. It’s great to see that my anecdotal experience is backed up, here. Because really, I’ve devoted a fuck ton of time to heat acclimation, and have been praising them for years.

As an elite endurance athlete, I’ve found my sauna usage to be extremely beneficial in recovery as well as performance enhancement. I train A LOT. A LOT. 5 days a week I’ll have a morning and afternoon session. One always is intense, the other not so much. ex. 10k run in the morning with a shorter 30-45 minute weight training session in the afternoon. The other 2 days it will generally be one long workout. After each session, I spend anywhere from 10-30 minutes in the sauna for both relaxation and recovery. People always ask me how I can do so much all the time and always bounce back so quickly. I think a big reason is my consistent sauna sessions.

In regards to the questions regarding the differences between the sauna and the steam room, I have experimented with both and from my experience, the steam room can have the same benefits, but it’s also harder to handle mentally as it generally “feels” hotter than the sauna due to the humidity. I’ve actually done some experimentation to calculate the differences in dehydration between the two and I can definitively say, at least for me, that the steam room can significantly dehydrate you more in the same amount of time than the sauna.

But with all that being said, enjoy the sauna but heed those warnings about being smart about it. Drink lots of water and also replenish electrolytes afterwards. I like to slam a big can of coconut water afterwards!

Up to 7 days a week similar to Jason Lee (the commenter right before me). But most of the time it’s 5-6 days per week. It’s been 0-5 degrees where I live the last couple days so I’ve definitely been more just enjoying the sauna lately rather than using it for recovery 🙂

This was very interesting as my job is a strength and conditioning coach for mma fighters. The method of training these guys go through is unbelievable ALL the way up to weigh ins which in some cases require these woman or men the train hard and need to cut weight and use a sauna for cutting the last few pounds. I was very impressed with the other methods that a sauna can provide. I’m going to be working this new information into my athletes training and not just for weight cuts. Thank you.

I used to sit in a Jacuzzi for 5-10 minutes, then swim a lap or two in 70 degree water then sit in the sauna for about 10 minutes and finish with ice cold shower for 30 seconds. I felt amazing after and this was done 3x/week usually. I find that the mixture of hot/cold/hot/cold really helps with recovery.

I am curious how sweating with exercise vs sweating with sauna plays a role..?

i wonder if one would get the same hyperthermic benefits from hot baths, or specifically ginger baths. i just tried a ginger bath recently and felt like it was way more intense than the infrared sauna i’d been going to. any thoughts?

Permanent or temporary gains? Why has no one asked this yet haha. So if you did 3 or 4 times per week at 30-45 minutes or went all out for 7 days straight 1 hour per day or 1 hour twice per day, are the benefits permanent or temporary?

16 fold increase in HGH so does that mean you will permanently produce more HGH or its just for a couple hours or days after the 3 week or 1 week period.

Same question for the effects on the Brain, do you experience permanent ability for neurogenisis and the other effects?

So if you did the this protocol either the 3 week or the 1 week thing do you permanent keep any of these gains and to what degree.

Because who has time to do this continuously throughout their life, especially if FIR saunas won’t produce the effects.

To answer you question in short, no – these results are not permanent if you do not continuously subject your body to them. It’s the use it or lose it principle, like everything in the human body.

Example: Weight Lifting. Once you stop lifting weight or training for that matter, atrophy (loss of muscle mass) occurs. Heat stress (or hyperthermic conditioning) is identical. If you do not continuously subject your body to this stimulus, you will not continuously produce the added benefits.

Same thing applies to adapting to altitude/hypoxia. Individuals that travel to roughly 2,500 m above sea level, acquire the benefits seen with altitude training (EPO production increases, RBC count increases, etc) – however – on return to sea level, the increase that they acquired will go back to baseline measurements within ~20-30 days.

THANK YOU, I was thinking about this a lot but now I don’t need to because anybody with a life would find it entirely impossible to accomplish this, not only that you would have to spend a crap ton of money at a Turkish Bath house cause they’re the only ones with Saunas that get that hot.

This crap is just like cold thermogenisis from Jack Kruse. I have notice a trend lately with Guru’s, they tell us stuff with amazing benefits that impossible to pull off just so they can get traffic to their websites or otherwise make money off of people.

Just please tell us stuff that is feasible atleast, I would be willing to pay for that.

I would wager that the discussion should and would pivot to epigentics and if the long time stimulus can and will improve the availability of genetic markers for positive and adaptive biochemical changes.

Conclusions: 3 wk of post-exercise sauna bathing produced a endurance enhancement for running specific, postulated to be contributed to the increase in blood volume.

[My Comments]: The authors didn’t look at anything from a hormonal standpoint, but it gives the notion that you would see both benefits towards IGF-1 production and also increasing insulin sensitivity post-exercise.